A MAC protocol of cognitive networks based on IEEE 802.11

Cognitive Radio permits the secondary users to share the spectrum in the space and time domain. But only while the primary users don´t occupy the spectrum, the secondary users could access. In addition to the dynamic nature of the spectrum environment, Media Access Control (MAC) spectrum access protocol design is facing several important issues. The secondary users need to determine when and which channel access to send/receive data without interference with the primary users. First, a detailed classification of the MAC protocols is presented, while considering the infrastructure support, integration of spectrum sensing functionalities, the need for time synchronization, and the number of radio transceivers. Then, A MAC protocol is proposed for the secondary radio based 802.11 networks. Specifically, the cognitive MAC protocols allow secondary users to identify and use the available frequency spectrum without interference with the primary users. This paper proposes a Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) MAC protocol to enable the secondary users dynamically utilize the available frequency spectrum, and analyses its performance. Finally the conclusion is presented.